1. Field of the Invention
The present invention is directed generally to mixing devices and more particularly to mixing devices that mix two or more materials between surfaces, including such as between a rotating rotor and a stationary stator.
2. Description of the Related Art
FIG. 1 provides a partial block diagram, partial cross-sectional view of a prior art device 10 for diffusing or emulsifying one or two gaseous or liquid materials (“infusion materials”) into another gaseous or liquid material (“host material”) reproduced from U.S. Pat. No. 6,386,751, incorporated herein by reference in its entirety. The device 10 includes a housing configured to house a stator 30 and a rotor 12. The stator 30 encompasses the rotor 12. A tubular channel 32 is defined between the rotor 12 and the stator 30. The generally cylindrically shaped rotor 12 has a diameter of about 7.500 inches and a length of about 6.000 inches providing a length to diameter ratio of about 0.8.
The rotor 12 includes a hollow cylinder, generally closed at both ends. A gap exists between each of the first and second ends of the rotor 12 and a portion of the housing 34. A rotating shaft 14 driven by a motor 18 is coupled to the second end of the rotor 12. The first end of the rotor 12 is coupled to an inlet 16. A first infusion material passes through the inlet 16 and into the interior of the rotor 12. The first infusion material passes from the interior of the rotor 12 and into the channel 32 through a plurality of openings 22 formed in the rotor 12.
The stator 30 also has openings 22 formed about its circumference. An inlet 36 passes a second infusion material to an area 35 between the stator 30 and the housing 34. The second infusion material passes out of the area 35 and into the channel 32 through openings 22.
An external pump (not shown) is used to pump the host material into a single inlet port 37. The host material passes through a single inlet port 37 and into the channel 32 where it encounters the first and second infusion materials, which enter the channel 32 through openings 22. The infusion materials may be pressurized at their source to prevent the host material from passing through openings 22.
The inlet port 37, is configured and positioned such that it is located along only a relatively small portion (<about 5%) of the annular inlet channel 32, and is substantially parallel to the axis of rotation of the rotor 12 to impart an axial flow toward a portion of the channel 32 into the host material.
Unfortunately, before entering the tubular channel 32, the host material must travel in tortuous directions other than that of the axial flow (e.g., including in directions substantially orthogonal thereto) and down into and between the gap formed between the first end of the rotor 12 and the housing 34 (i.e., down a portion of the first end of the rotor adjacent to the inlet 16 between the end of the rotor 12 and the housing 34). The non-axial and orthogonal flow, and the presence of the host material in the gap between the first end of the rotor 12 and the housing 34 causes undesirable and unnecessary friction. Further, it is possible for a portion of the host material to become trapped in eddy currents swirling between the first end of the rotor and the housing. Additionally, in the device 10, the host material must negotiate at least two right angles to enter any aspect of the annual of the annular inlet of the tubular channel 32.
A single outlet port 40 is formed in the housing 34. The combined host material and infusion material(s) exit the channel 32 via the outlet 40. The outlet port 40, which is also located along only a limited portion (<about 5%) of the annular outlet of tubular channel 32, is substantially parallel to the axis of rotation of the rotor 12 to impart or allow for an axial flow of the combined materials away from the limited portion of the annular outlet of tubular channel 32 into the outlet port 40. An external pump 42 is used to pump the exiting fluid through the outlet port 40.
Unfortunately, before exiting the channel 32, a substantial portion of the exiting material must travel in a tortuous direction other than that of the axial flow (e.g., including in directions substantially orthogonal thereto) and down into and between the gap formed between the second end of the rotor 12 and the housing 34 (i.e., down a portion of the second end of the rotor adjacent to the shaft 14 between the end of the rotor 12 and the housing 34). As mentioned above, the non-axial and orthogonal flow, and the presence of the host material in the other gap between the end (in this case, the second end) of the rotor 12 and the housing 34 causes additional undesirable and unnecessary friction. Further, it is possible for a portion of the host material to become trapped in eddy currents swirling between the second end of the rotor and the housing. Additionally, in the device 10, a substantial portion of the exiting combined material must negotiate at least two right angles as it exits form the annular exit of the tubular channel 32 into the outlet port 40.
As is apparent to those of ordinary skill in the art, the inlet port 37 imparts only an axial flow to the host material. Only the rotor 21 imparts a circumferential flow into the host material. Further, the outlet port 40 imparts or provides for only an axial flow into the exiting material. Additionally, the circumferential flow velocity vector is imparted to the material only after it enters the annular inlet 37 of the tubular channel 32, and subsequently the circumferential flow vector must be degraded or eliminated as the material enters the exit port 40. There is, therefore, a need for a progressive circumferential acceleration of the material as it passes in the axial direction through the channel 32, and a circumferential deceleration upon exit of the material from the channel 32. These aspects, in combination with the tortuous path that the material takes from the inlet port 37 to the outlet port 40, create a substantial friction and flow resistance over the path that is accompanied by a substantial pressure differential (26 psi, at 60 gallons/min flow rate) between the inlet 37 and outlet 40 ports, and these factors, inter alia, combine to reduce the overall efficiency of the system.